Method for arranging and growing high-density boron nitride nanotubes

Abstract

The invention discloses a method for arranging and growing high-density boron nitride nanotubes. According to the method, a three-stage surface engineering scheme of polishing, grooving and cleaning is combined with high-temperature annealing assistance, so that the boron nitride nanotube film which is arranged and grown in a high-density manner can be obtained. Pollution on the surface of the substrate is removed through electrochemical polishing, the nucleation number of the boron nitride nanotubes is increased, and the purposes of airflow orientation and surface wetting of reactants are achieved in cooperation with micro-nano groove etching and plasma cleaning design. In a high-temperature environment, the arrangement and growth of the high-density boron nitride nanotubes are realized by controlling the magnitude of shearing force generated by the airflow velocity. The boron nitride nanotube arrangement growth process provided by the invention is simple and low in cost, and provides possibility for efficient application of the boron nitride nanotube material in various fields.

Description

Technical Field

[0001] The invention belongs to the field of materials and relates to a method for growing boron nitride nanotubes, in particular to a method for arranging and growing high-density boron nitride nanotubes. Background Art

[0002] In the field of infrared optical devices, the selective absorption, polarization modulation and transmission performance of materials for wide-band infrared radiation are the key to achieving high-sensitivity detection and high-resolution imaging. Although the traditional metal grating structure can produce obvious polarization effect in the mid-infrared band, its surface free electron resonance brings high light loss and strong temperature drift, which limits the stability and bandwidth expansion of the device. In addition, the metal structure is prone to cracking or morphological distortion under flexible deformation conditions, resulting in the degradation of polarization characteristics. In contrast, the high-density boron nitride nanotubes grown in an arranged manner exhibit significant anisotropic infrared absorption and transmission characteristics in the range of 3–20 μm due to their one-dimensional ordered orientation and high crystal quality. Their phonon polariton resonance mode not only has an extremely narrow absorption bandwidth, but also can achieve tunable bandwidth and resonance peak position by adjusting the diameter, spacing and array height of the nanotubes. Although boron nitride nanotubes have excellent performance in theory, their preparation process is still immature. The existing methods are cumbersome, low in yield and uneven in structural distribution, making it difficult to achieve high-density and orderly arranged growth. This key technical bottleneck needs to be broken through urgently to fully release the application potential of BNNTs in various fields. The present invention adopts a simple and efficient method to achieve high-density arranged growth of boron nitride nanotubes, providing solid technical support for the development of next-generation broadband, tunable, flexible infrared optical devices. Summary of the invention

[0003] The purpose of the invention is to provide a method for arranging and growing high-density boron nitride nanotubes.

[0004] The above technical problem of the present invention is solved by the following scheme.

[0005] The invention discloses a method for arranging and growing high-density boron nitride nanotubes, comprising: electrochemical polishing, micro-nano groove processing and plasma cleaning of the metal substrate surface, and then utilizing air flow shear force control and high-temperature annealing to achieve the growth of boron nitride nanotubes.

[0006] In the above method, the metal substrate is 316 stainless steel, and the stainless steel base is 316 stainless steel with a thickness of 1-2 mm.

[0007] The polishing liquid of the electrochemical polishing process includes deionized water, phosphoric acid, ethanol, isopropanol and urea in a ratio of 9:10:5:2. The volume of the commonly used polishing liquid can be 300 mL, and the amount of urea is 0.8-1.0 g per 100 mL of the total amount of other components.

[0008] The electrochemically polished voltage is 12 - 18V; specifically 15V;

[0009] The current is 2 - 5A; specifically 4A;

[0010] The time is 10 - 25min; specifically 20min.

[0011] The micro - nano groove machining is completed by a rolling and polishing device, with the groove width of about 400 - 800nm and the depth of about 80 - 150nm.

[0012] The plasma cleaning is carried out using an O2 / Ar mixed atmosphere for plasma cleaning, and the cleaning is performed 1 - 3 times.

[0013] In the growth step, the temperature is 1100 - 1250°C;

[0014] The heating rate is to heat to 1100 - 1250°C in 30 - 40min; specifically, it can be heating to 1100°C in 40min;

[0015] Maintain at 1100°C for 10 - 60min; specifically 40min;

[0016] The gas flow used is a mixed gas of nitrogen and hydrogen, and the ratio is 1 - 20:1 - 10; specifically 9:1;

[0017] The flow rate of the nitrogen and hydrogen mixed gas is 10 - 60sccm; specifically 30sccm.

[0018] In the growth step, the reactant used is boron powder; specifically high - purity nano - boron powder;

[0019] In the growth step, the catalyst used is a dual - catalyst, specifically iron and alumina; more specifically nano - iron and nano - alumina. The method further includes: after the growth is completed, quickly cool the tubular furnace to 100°C, then turn off the hydrogen, and stop the supply of the nitrogen and hydrogen mixed gas after cooling to room temperature.

[0020] In addition, the growth of high - density boron nitride nanotubes arranged according to the above - mentioned method also belongs to the protection scope of the present invention. Brief Description of the Drawings

[0021] Figure 1 It is an image of high - density arranged and grown boron nitride nanotubes prepared in Example 1.

[0022] Figure 2 It is a scanning electron microscope image of the arranged and grown boron nitride nanotubes prepared in Example 1.

[0023] Figure 3This is the Raman spectrum of the aligned and grown boron nitride nanotubes prepared in Example 1.

[0024] Figure 4 This is a scanning electron microscope image of the core stage of the aligned and grown boron nitride nanotube cluster prepared in Example 2.

[0025] Figure 5 This is a scanning electron microscope image of the boron nitride nanotubes prepared in Comparative Example 1.

[0026] Figure 6 This is a scanning electron microscope image of the cluster core stage of boron nitride nanotubes prepared in Comparative Example 1. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below by way of embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] Example 1

[0029] First, the metal substrate (2×1.5cm) was electrochemically polished with a polishing solution consisting of 104mL of deionized water, 115mL of phosphoric acid, 58mL of ethanol, 23mL of isopropanol and 2.8g of urea; after polishing, ultrasonic cleaning was performed for 10min, and the substrate was dried with nitrogen and then grooved using a roller press; ultrasonic cleaning was performed again for 10min, and plasma cleaning (O2 / Ar mixed atmosphere) was performed after drying with nitrogen; the surface was infiltrated with reactants; after the tubular furnace was heated to 1100°C, the metal substrate infiltrated with the reactants was placed in the center of the tubular furnace, and a nitrogen and hydrogen mixed gas with a flow rate of 30sccm was introduced for 40min, and then the introduction of the nitrogen and hydrogen mixed gas was stopped when the substrate was cooled to room temperature, and the growth was completed.

[0030] Figure 1 This is the stainless steel substrate (in the corundum boat) taken out from the tube furnace after the tube furnace is cooled to room temperature in this embodiment. The white surface is the boron nitride nanotubes that are densely arranged and grown; Figure 2 This is a scanning electron microscope image of the aligned and grown boron nitride nanotubes prepared in this example, where the boron nitride nanotubes are intertwined and grow in the same direction; Figure 3 for Figure 1 This is a Raman spectrum of the high-density aligned and grown boron nitride nanotubes prepared in this example.

[0031] Example 2

[0032] Electrochemically polish the metal substrate (2×1.5 cm). The polishing solution used consists of 104 mL of deionized water, 115 mL of phosphoric acid, 58 mL of ethanol, 23 mL of isopropanol, and 2.8 g of urea; after polishing, ultrasonically clean for 10 min, blow-dry the substrate with nitrogen, and then use a rolling equipment to groove the surface; ultrasonically clean again for 10 min, blow-dry with nitrogen, and then perform plasma cleaning (O2 / Ar mixed atmosphere); infiltrate the surface with reactants; after the tube furnace is heated to 1100 °C, place the metal substrate infiltrated with reactants in the center of the tube furnace, introduce a mixed gas of nitrogen and hydrogen with a flow rate of 25 sccm, hold for 50 min, cool to room temperature, and stop introducing the mixed gas of nitrogen and hydrogen, and the growth ends.

[0033] Figure 4 This is the scanning electron microscope image of the aligned-growth boron nitride nanotubes prepared in this example, which grow in one direction starting from the nucleation point (the standard deviation of the orientation angle <5°).

[0034] Comparative Example 1

[0035] Electrochemically polish the metal substrate (2×1.5 cm). The polishing solution used consists of 104 mL of deionized water, 115 mL of phosphoric acid, 58 mL of ethanol, 23 mL of isopropanol, and 2.8 g of urea; after polishing, ultrasonically clean for 10 min, blow-dry the substrate with nitrogen, and then infiltrate the surface with reactants; after the tube furnace is heated to 1100 °C, place the metal substrate infiltrated with reactants in the center of the tube furnace, introduce a mixed gas of nitrogen and hydrogen with a flow rate of 25 sccm, hold for 50 min, cool to room temperature, and stop introducing the mixed gas of nitrogen and hydrogen, and the growth ends.

[0036] Figure 5 This is the scanning electron microscope image of the boron nitride nanotubes prepared in this comparative example. It can be found that without grooving and plasma cleaning, the boron nitride nanotubes do not have the characteristics of aligned growth; Figure 6 This is the scanning electron microscope image of the growth stage of the cluster nucleus in this comparative example. It can be found that the boron nitride nanotubes grow disorderly starting from the nucleation point.

[0037] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0038] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for growing a high-density arrangement of boron nitride nanotubes, characterized in that: After the surface of the metal substrate is electrochemically polished, micro-nano groove processed, and plasma cleaned, the reactants are infiltrated on the substrate surface, and then high-density growth of boron nitride nanotubes is completed in combination with high-temperature annealing.

2. The method for growing a high-density arrangement of boron nitride nanotubes according to claim 1, wherein: The stainless steel substrate is 316 stainless steel with a thickness of 1-2 mm.

3. A method for growing a high-density arrangement of boron nitride nanotubes according to any one of claims 1-3, characterized in that: The electrochemically polishing voltage is 12-18 V; specifically 15 V; The current is 2-5 A; specifically 4 A; The time is 10-25 min; specifically 20 min.

4. A method for growing a high-density arrangement of boron nitride nanotubes according to claim 1, wherein: The micro-nano groove processing is completed by a rolling and polishing device, and the groove width is about 400-800 nm and the depth is about 80-150 nm.

5. A method for growing a high-density arrangement of boron nitride nanotubes according to claim 1, characterized in that: The plasma cleaning is carried out by using an O2 / Ar mixed atmosphere for plasma cleaning, and the cleaning is carried out 1-3 times.

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